Current Transformers (CTs)

CTs are used to measure the amount of current that flows through a wire. The split-core CTs that we stock are convenient to install since they can be opened up and slipped over the wire, without requiring disconnecting the wire first.

CTs have two ratings:

Current:

The current rating specifies the maximum current that the CT can measure accurately. If the current through the wire exceeds the rating of the CT, it will saturate. For example, if a 200A current were flowing in a wire through a 100A CT, then the CT might only report a current of 180A. On the other hand, CTs also loose some accuracy if the current through the wire is below 10% of the rated current. Because of this, it is best to choose a CT that's just big enough to measure the biggest expected current. Having said that, 100A CTs generally work very well for most residences and solar systems. For more details on choosing CTs of appropriate current rating, see the "CT Selection Guide" available in the Support section of this site.

Size:

The size rating of the CT is the inner dimension (ID) of the hole in the center of the CT. This rating simply needs to be big enough so that the CT can fit over the wire whose current is to be measured. We stock CTs with an ID size rating of 0.75", 1.25", and 2". Bigger CTs and bus-bar CTs are available upon request. Keep in mind that the exterior dimension of CTs with larger size rating are proportionally bigger too, so be sure to verify that the CTs fit inside the enclosure that they to be mounted in.

The CTs we carry are UL recognized components as well as CE and ROHS certified.

Data Sheets

• 0.40" CTs
• 0.75" CTs
• 1.25" CTs
• 2.00" CTs